Heart disease presents a major concern in western societies. Heart disease may cause chest pains, strokes, heart attacks, or even death. One form of heart disease is ischemic heart disease, a condition where the heart or myocardium does not receive an adequate nutritive blood supply. Typically, this condition occurs when the coronary arteries become blocked by plaque build-up on their inner walls.
When the plaque build-up of the coronary arteries hinders the flow of blood to the heart, the heart may become starved for nutrition and oxygen. As a result, the tissue of the heart may scar, causing the heart to be weakened.
A number of approaches have been developed for treating heart disease. In less severe cases, proper diet and exercise may improve heart conditions. However, if diet and exercise are not effective, medication may be prescribed. If heart disease still persists, a minimally invasive or invasive procedure is usually performed.
There are several types of traditional medical procedures that may be used to improve blood supply to the heart. For example, coronary bypass surgery or percutaneous transluminal coronary angioplasty (PTCA) may be performed to increase blood flow to the heart.
Coronary bypass surgery involves open heart surgery where a surgeon removes a blood vessel from another part of the body, such as the leg or inside the chest wall, and uses the vessel to construct a detour around the blocked coronary artery. One end of the vessel is attached below the blockage while the other end is attached above the blockage. As a result, blood may flow around the obstruction into the heart.
However, because bypass surgery typically requires extensive and complicated surgery, the patient needs to have adequate lung and kidney function in order to tolerate such surgery. This procedure also requires postoperative care in an intensive care unit, seven to ten days in the hospital, and several months of recovery. Other complications, such as strokes, heart attacks, or infections, may develop during or as a consequence of the surgery. In addition, the blood vessel may close or become blocked several months after the surgery.
In PTCA, a surgeon inserts a thin wire through a small incision in an arm or leg artery of a patient and threads the wire toward the blocked area of the coronary artery. Next, a guide catheter may be passed over the wire and a balloon-tipped catheter is usually threaded through the guide catheter. When the balloon-tipped catheter reaches the blockage area, the balloon is inflated to compress the plaque build-up against the coronary artery walls, widening the artery for blood flow. The balloon-tipped catheter may then be deflated and withdrawn from the patient.
If the artery closes or threatens to close, a balloon catheter having a mesh stent may be used. As the stented balloon inflates, the mesh of the stent expands and remains in place to hold the artery open after the balloon catheter has been removed.
More recently, Laser Transmyocardial Revascularization (LTR) has been used as an alterative to coronary bypass surgery or PTCA. This technique is used to supplement the blood supply received by the heart by providing the myocardium direct access to blood in the ventricle chamber. In one known approach, LTR is performed using a high power, pulsed, CO.sub.2 laser. The laser may be operated to create a channel from the ventricle to the myocardium. The laser is fired against the outer ventricle surface of the heart when the ventricle is full of blood. The blood in the ventricle acts as a backstop preventing the energy of the laser from penetrating through the other side of the ventricle or damaging nearby tissue. After a channel is formed, blood may flow through the resulting channel from the ventricle into the myocardium.
However, the cost of the laser is quite high, as is the cost of the procedure. The laser is ordinarily quite large and takes up significant space in the operating room. In addition, LTR is not always easily adaptable for thoracoscopic heart surgery and usually requires a 2.5 cm minithoracotomy. Furthermore, LTR ordinarily requires an EKG to synchronize the firing of the laser when the heart is full of blood to absorb the laser beam.
Ultrasonic devices are also known for assisting a surgeon in cutting tissue. For example, U.S. Pat. No. 5,449,370 entitled "Blunt Tipped Ultrasonic Trocars," which is herein incorporated by reference, discloses a trocar to puncture an abdominal wall of a patient. U.S. Pat. No. 5,324,299 entitled "Ultrasonic Scalpel Blade And Method Of Application," which is incorporated herein by reference, discloses an ultrasonic device including a blade portion having a recess that defines a hook for grasping and tensioning loose tissue to facilitate cutting. U.S. Pat. No. 5,322,055 entitled "Clamp Coagulator/Cutting System For Ultrasonic Surgical Instruments," which is incorporated herein by reference, also discloses a surgical instrument for cutting tissue. The instrument includes an ultrasonic blade for use with a clamp to improve tissue cutting.
Accordingly, there is a need for devices and methods to treat heart disease. It would be beneficial to provide devices and methods to achieve a more effective treatment of heart disease. It would also be desirable to provide a cost-effective and minimally intrusive procedure to improve blood flow to the heart.